Implants, such as artificial tooth roots, artificial hip joints, artificial knee joints, and bone connecting materials, which are implanted in living bodies have become more and more important in aging society. As base materials for the implants, titanium and titanium alloys are employed for their high affinity for living bodies, high corrosion resistance, and high mechanical strength. Titanium and titanium alloys, however, are not bonded to living bone tissues, and thus, are not integrated with living bones. If titanium and titanium alloys are implanted in living bodies for a long period, loosening and/or shear can occur. To bond an implant to living bone tissues, there has been an attempt to coat the surface of a base material for an implant with a material having affinity for living bodies.
Hydroxyapatite is most generally used for coating of implants. However, hydroxyapatite has poor adhesion to base materials such as titanium. Accordingly, implants coated with hydroxyapatite have low stability and low durability.
There has also been an attempt to use a diamond-like carbon film (a DLC film) as a coating of an implant (see, for example, Patent Document 1). The DLC film has high adhesion to a base material such as titanium, and thus, can form a stable coating.